Process for dyeing cellulose derivative textile material by impregnating it with a swelling solution containing urea and an esterified leuco vat dye and subsequently steaming twice



Patented @ct. M, 1%52 STATES an on TENT -FFICE STEAMING TWICE Henry Charles Glpin and Tom Jackson, Spondon, near Derby, England, assignors to Celanese Corporation of America, a corporation of Delaware No Drawing. Application February 12, 1949, Se-

rial No. 76,187. In Great Britain February 23,

6 Claims.

This invention relates to the coloration of textile fibres of cellulose acetate or other cellulose ester or other and is more particularly concerned with eiiecting the coloration by means of vat dyes applied in the form of esters of their leuco compounds with (11- or poly-basic acids, for example sulphuric acid or phosphoric acid. The'invention is particularly concerned with the coloration of cellulose acetate fibres and will be more especially described with reference to the coloration of this material.

Cellulose acetate fibres can be colored in a wide range of shades of very good fastness properties by the aid of solutions of esters of the leuco compounds of vat dyes with di- "or poly-basic acids such as sulphuric or phosphoric acid, the solutions being in aqueous liquid media of which a substantial. portion is an organic liquid; the media are preferably such as are capable of swelling the cellulose acetate fibres. The ester of the leuco vat dye, hereinafter referred to as the leuco ester, is thus incorporated in the cellulose acetate fibres and can 'be converted therein to the parent vat dye by a suitable acidoxidising treatment. Such methods of using the leuco esters for the coloration of cellulose acetate fibres are described, for instance, in U. S. Patents Nos. 2,218,628 and 2,248,835.

It has now been found that it is very advantageous to'include a proportion of urea in the solution of the leuco ester in the organic liquid medium, and to steam the material after impregnatien with the liquid. One advantage of the inclusion of urea is that a better col-or yield is obtained, that is to say, a fuller shade can be obtained with a given proportion of dye than when the urea is omitted. Another merit is that the shades obtained when urea is included more nearly approach those which the parent vat dyes yield on cellulose by conventional vat-dyeing processes. In the absence of urea it is sometimes found that the shade obtained after oxidation of the leuco ester on the material is substantially different from the true shade of the dye. This diiference in shade is almost invariably in the direction of an undesirable greyness and lack of brilliance.

According to the present invention, therefore, a process for the coloration of cellulose ester or ether textile material comprises impregnating the material with a solution of an ester of a leuco vat dye in a mixture of water and an organic liquid containing urea, and thereafter steaming the material and converting the ester to the parent vat dye. The organic liquid content of the liquid medium can be of an organic hydroxy compound, ket-one, ester or ether, and may be of a compound containing two or more groups or atoms of the kind commonly referred to as polar. Thus it may be a compound containing a hydroxy group together with a polar group or atom of another kind, for example a keto group-CO, an ester group-'COO-, an ether oxygen-O or a halogen atom.

Water-miscible alcohols, for example, ethyl alcohol, methyl alcohol or a propyl or butyl alcohol, have been found particularly useful as the organic liquid content of the organic liquid medium containing the leuco ester. Other liquids which may be used are acetone, methyl-ethyl ketone, diacetone-alcohol, partial carboxylic esters of aliphatic dior poly-hydric alcohols, e. g. glycol monoacetate and glycerol diaceta-te, partial ethers of aliphatic dior poly-hydric alcohols, e. g. glycol monomethyl or monoethyl ether, esters of hydroxy carboxylic acids, e. g. ethyl lactate, halogen hydrins, e. g. ethylene chlorhydrin or propylene chlorhydrin, water-miscible ethers, e. g. ethylene'methylene ether, and ether-esters, for example glycol monomethyl ether acetate.

As already indicated, the liquid medium contains water, the best proportion of which depends upon the particular organic liquid which is being employed. The mixture'of water and organic liquid should be capable of swelling the cellulose acetate fibres but without, of course, damaging them. Thus, when using water-miscible alcohols, for example ethyl, methyl or propyl alcohols, the latter may constitute from to 75% by Weight, particularly 60% to 70% of the water and alcohol together. Many of the other liquids enumerated above are solvents for cellulose acetate, and they should be used in lower proportions than indicated above in connection with the alcohols. For instance, it is not usually necessary or desirable to exceed about 25% in the case of diacetone alcohol, glycol monomethyl ether acetate, or ethyl lactate. A lower proportion may be used, but in general a proportion of at least 10% is desirable for good results.

The organic liquid medium may with advantage contain a thiocyanate, for example ammonium, sodium or potassium thiocyanate. The proportion may be from 1% upwards, e. g. 1 to 5%, based on the weight of the organic liquid medium, and, in the case of using aqueous meth-- yl, ethyl or propyl alcohol of %-'75% strength,

may advantageously be from 1% to 5%, based on.

the weight of the aqueous alcohol. A particularly useful medium for the application of the leuco esters is aqueous ethyl alcohol of from to strength containing about 3% of ammonium thiocy-anate. 1

As regards the urea, very good results are ob tained with from 5% to 20%, particularly to based on the weight of the organic liquid medium. The latter may, for instance, consist of aqueous ethyl alcohol of from 60% to 70% strength containing about 3% of ammonium thiocyanate and about 13% of urea, both being based on the weight of the aqueous ethyl alcohol. In the place of urea, its alkyl derivatives such as are water-soluble may be used. Again, the urea may be replaced by water-soluble amides of carboxylic acids, for example formamide, acetamide and their water-soluble homologues, or watersoluble esters of carbamic acid, for example ethyl carbamate, that is ethyl urethane.

The cellulose acetate fibres to be colored in accordance with the present invention may be in various forms. Thus they may be in the form of continuous filament yarns or fabrics containing such yarns, or in the form of staple fibres, e. g. in the form of a. loose mass of staple fibre or a staple fibre yarn or a fabric composed of such staple fibre yarn. They may also be in association with other textile fibres in various ways, and especially in the form of fabrics woven from on the one hand cellulose acetate yarns and on the other hand yarns of cotton or regenerated cellulose.

The application of the solutions of the leuco esters to the cellulose acetate fibres may be effected in various ways. In general, it is most convenient and effective to use mechanical impregnation methods, that is methods in which a predetermined proportion of the dye liquid is applied to the material and the proportion thereon adjusted by squeezing, centrifuging or the like until there remains thereon the proportion requisite for the desired shade. Thus, printing or padding methods may be used. For printing purposes the solutions of the leuco esters may be suitably thickened, e. g. with a water soluble methyl cellulose as described in U. S. application S. No. 592,725, filed May 8, 1945, now Patent 2,514,410.

It is also frequently advantageous to eifect some degree of thickening for application by other mechanical impregnation methods such as padding.

Following the impregnation of the textile material with the solution of the leuco ester the material is preferably dried and then subjected to steaming. The leuco ester is thereby carried within the cellulose acetate fibres, and, upon subsequent development by oxidation, the parent vat dye is formed within the fibres and not on the surface. The steaming may be efiected at 105- 110 C. or higher for a period of the order of to 60 minutes; minutes at 107 C. has been found very eifective.

The conversion of the leuco ester on the material to the parent vat dye can be effected by a suitable acid-oxidising treatment. An aqueous oxidising bath prepared with 1-2 grams of sodium nitrite and 10-30 ccs. of concentrated sulphuric acid per litre is very effective. Acidified chromate solutions may also be used.

Following the oxidation treatment, the material should be washed and is then preferably soaped at, say, 70 C. Further, it has been found very advantageous to steam the material after development of the vat dye by the acid-oxidation. This steaming, which may be efiected at temperatures and times similar to those indicated above for the steaming of the material carrying the leuco ester, serves to modify the physical form of the vat dye in the cellulose acetate material. The result is usually a further improvement in shade, particularly towards obtaining the true shade of the vat dye and, perhaps more important still, a considerable improvement in the fastness to light of the ultimate dyeing. It has been found, for instance, that this final steaming operation may result in improving the light-fastness by more than one unit on the S-scale, that is to say, the steamed dyeing will withstand more than twice as much exposure to light as will the unsteamed dyeing.

A wide range of leuco esters may be applied to cellulose acetate fibres by the new process. The parent vat dyes may belong to the indigoid series or to the anthraquinone series, and the following are examples of specific leuco esters which have given good results:

Indigosol Golden Yellow IRK Soledon Red 3138 Indigosol Priming Blue IGG Soledon Pink FFS Indigosol Brown 13B Soledon Jade Green 3B8 Indigosol Green IBS Soledon Jade Green XS Indigosol Printing Purple IR Soledon Blue ZRCS Indigosol Bordeaux I2RN Soledon Blue 4130 They may-be employed either singly or as mixtures.

All these products are sulphuric esters of leuco compounds of vat dyes of the indigoid or anthraquinone series. Indigosol Golden Yellow IRK is derived from brominated pyranthrone. Indigosol Printing Blue IGG is derived from 4,6-dichlor- 4'-methyl-7-methoxy-2-naphthalene-2'indoleindigo. Soledon Red 2B8 is derived from 5,5- dich1or-'7,7-dimethyl-thioindigo. Soledon Pink FPS is derived from 4,4-dimethyl-6,6-dichlorthioidigo. Soledon Jade Green 3B8 is derived from an allroxy-dibenzanthrone. Soledon Jade Green XS is derived from dimethoxy-dibenzanthrone. Soledon Blue 2RCS is derived from 3,3- dichlor-indanthrone. Soledon Blue 4130 is derived from 5:7,5:7-tetrabromindigo. Indigosol Green IBS and Indigosol Printing Purple IR. are referred to in Schultz, Farbostofftabellen, 7th edition, supplementary vol. I, page 108.

A very important application of the new process is for the coloring of textile fabrics containing both cellulose acetate fibres and cellulose fibres, whether of cotton or regenerated cellulose. Regenerated cellulose fibres may be those produced by the viscose or cuprammonium processes or those obtained by the substantially complete 'saponification of cellulose acetate fibres which have stretched to a high degree, particularly in wet steam or hot water. When a fabric containing both cellulose acetate fibres and cellulosefibres is processed in the manner indicated above, a more or less solid shade is obtained on the fibres. If, however, the material is thoroughly washed off after the first steaming treatment and before the acid-oxidising treatment, it is possible in most cases to remove the leuco ester substantially completely from the cellulose fibres while leaving it in the cellulose acetate fibres. Upon subsequently oxidising the material the cellulose acetate fibres are colored while the cellulose fibres are found to be substantially uncolored. Some leuco esters, however, have so much afilnity for cellulose fibres that they are not readily removed by washing or even by an extensive soaping treatment. They are, therefore, unsuitable for use in cases where it is desired to color the cellulose acetate with the leuco ester while leaving the cellulose uncolored. Products of this type are Indigosol Brown 13B, Indigosol Brown IBR and Indigosol Red IFBB.

After coloring the cellulose acetate fibres of a. mixed material containing both cellulose acetate fibres and cellulose fibres in the aforesaid manner, the cellulose fibres maysubsequently be colored in any convenient way, for example with direct cotton colors or by vat dyes applied from weakly alkaline vats or by means of leuco esters of the vat dyes. The latter are particularly convenient, since it is possible to utilise a single acid-oxidizing treatment to develop both the leuco ester on the cellulose acetate and the leuco ester on the cellulose fibres. To this end, the material is impregnated with the leuco ester solution containing the organic liquid and urea and is then steamed. The material is then, without oxidising, given a washing or soaping treatment to remove the leuco ester from the cellulose fibres. The material is then further impregnated with an aqueous solution of a leuco ester which does not swell the cellulose acetate, and the material is then subjected to acid-oxidation. By applying the same leuco ester to the cellulose fibres as to the cellulose acetate fibres but in a different proportion, two-tone efiects of the same shade can be obtained on the two fibres. Again, by applying a different leuco ester or mixture of leuco esters, the two fibres may be colored in different shades.

The invention has been described more particularly with reference to the coloring of cellulose acetate fibres. The new process can, however, be applied to the coloration of fibres of cellulose formate, propionate, butyrate, acetopropionate or acetobutyrate, or to fibres of cellulose ethers, for example ethyl cellulose.

The invention is illustrated by the following examples:

Example 1 A padding liquid is prepared of the following composition:

Methylated spirits ccs 67.5 Water ccs 22.5 Urea grarns Indigosol Golden Yellow IRK do 2 Ammonium thiocyanate do 2 The dye is dissolved in the methylated sprit and water containing the urea by heating, and to the cooled solution is added the ammonium thiocyanate. The temperature is adjusted to about 23 C., and a cellulose acetate fabric is padded with the solution so that it retains about 50% of its weight. of the solution, dried and steamed for two periods of about 20 minutes each at 107 C in a continuous steamer. The material is then oxidised in an aqueous solution of sodium nitrite (1 /2 gm./litre) acidified with 20 cos/litre of concentrated sulphuric acid, washed in cold water, and soaped at 70 C. for 20 minutes in a 2-gm./litre soap solution. A final steaming is then given, this being effected at 110 C. for 40 minutes. A full golden yellow shade is obtained.

Example 2 The following procedure is employed to obtain a two-color effect upon a jacquard fabric woven from a cellulose acetate warp and a cotton weft in a reversible leaf design. A solution is prepared of the following composition:

Methylated spirit .ccs 67.5 Water ccs 22.5 Urea grams 10.0 Soledon Red 3BS do 3.0 Indigosol Golden Yellow IRK do 1.8 Ammonium thiocyanate do 2.0

As in Example 1, the dyes are dissolved by heating in the spirit, water and urea and the ammonium thiocyanate added after cooling. The fabric is padded in the solution at about 23 C. so that it retains about 50% of its weight of the solution. After drying, the material is given two steamings of 20 minutes each at 107 C. in order to fix the leuco esters in the cellulose acetate. The material is then washed in cold water and soaped in a 2-gm./litre soap solution at 60 C. for 20 minutes or more, for the purpose of clearing the cotton fibres of the leuco esters. The material is again rinsed, dried, and padded in an aqueous solution containing 0.5 gram of Soledorr Jade Green XS and 0.175 gram of Indigosol Golden Yellow IRK per cos. of water. The padded material is dried and the vat dye developed on both the cellulose acetate and cotton in an aqueous bath prepared with 1.5 gm./litre of sodium nitrite and 20 cos/litre of concentrated sulphuric acid. Development is followed by washing with water and soaping. at 7 0 C. for 20 minutes, this serving to remove from the cellulose acetate any loose dye deposited thereon from the aqueous padding solution. Finally, the material is steamed at C. for 4.0 minutes. The cellulose acetate contents of the material is thus colored in a maroon shade while the cotton is colored in a green shade, the dye being effectively fixed to both fibres.

The leuco esters specified may be replaced by other leuco esters or mixtures thereof according to the particular shades required uponthe two fibres.

- Example 3 A printing paste is prepared by dissolving 25 grams of water-soluble methyl cellulose (viscosity 450 centipoises measured in 2% aqueous solution at 25 C.) in a solution of 100 grams of urea in a mixture of 675 cubic centimeters of methylated spirit and 225 cubic centimeters of water. 35 grams Indigosol Bordeaux I2RN and 5 grams Indigosol Golden Yellow IRK are dissolved in this paste by heating, and to the cooled solution are added 40 grams of ammonium thiocyanate.

A cellulose acetate fabric is printed with this paste in a suitable design, and is then dried and steamed for forty minutes at 107 C. It is then oxidised in an aqueous solution of 1 grams per litre sodium nitrite acidified with 20 cc. per litre concentrated sulphuric acid. The resulting print is washed in cold water, and then soaped at 70 C. for 20 minutes in a 2 gram per litre soap solution. After drying it is given a final steaming treatment at 110 C. for 40 minutes.

Having described our invention, what we desire to secure by Letters Patent is:

1. Process fOr the coloration of textile material of a cellulose derivative selected from the group consisting of cellulose esters and cellulose ethers, which comprises impregnating the material with a solution of an ester of a leuco vat dye in a mixture of water and an organic liquid containing urea, the said mixture of Water and organic liquid being a swelling agent for the cellulose derivative, and thereafter steaming the material, converting the ester to the parent vat dye, and again steaming the material.

2. Process for the coloration of cellulose acetate textile material which comprises impregnating the material with a solution of an ester of a leuco vat dye in a mixture of water and an organic liquid containing urea, the said mixture of water and organic liquid being a swelling agent for the cellulose derivative, and thereafter steaming the material, converting the ester to the parent vat dye, and again steaming the material.

3. Process for the coloration of cellulose acetate textile material which comprises impregnating the material with a solution of an ester of a leuco vat dye in a mixture of water and an organic liquid containing urea, the mixture of water and organic liquid being a swelling agent for the cellulose acetate, and thereafter drying and steaming the material, converting the ester to the parent vat dye, and again steaming the material.

4. Process for the coloration of cellulose acetate textile material which comprises impregnating the material with a solution of an ester of a'leuco vat dye in a mixture of water and a Watermi'scible alcohol of from 1-3 carbon atoms, said mixture containing urea, and thereafter steaming the material, converting the ester to the parent vat dye, and again steaming the material.

5. Process for the coloration of cellulose acetate textile material which comprises impregnating the material with a solution of an ester of a leuco vat dye in aqueous ethyl alcohol of 50-75% strength containing urea and a thiocyanate, and thereafter steaming the material, converting the ester to the parent vat dye, and again steaming the material.

6. Process for the coloration of cellulose acetate textile material which comprises impregnating the material with a solution of an ester of a leuco vat dye in aqueous ethyl alcohol of 60-70% strength by weight containing 10-15% of urea and about 3% of ammonium thiocyanate based on the weight of the water and alcohol together,

8 and thereafter steaming the material, converting the ester to the parent vat dye, and again steaming the material.

HENRY CHARLES OLPIN. TOM JACKSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,816,766 Niederhausern July 28, 1931 1,963,974 Ellis June 26, 1934 1,968,856 Rivat Aug. 7, 1934 2,080,254 Dreyfus May 11, 1937 2,291,052 Miller July 28, 1942 2,428,835 Croft Oct. 14, 1947 2,428,836 Croft Oct. 14, 1947 FOREIGN PATENTS Number Country Date 285,948 Great Britain Feb. 13, 1928 592,858 Great Britain Oct. 1, 1947 594,722 Great Britain Nov. 18, 1947 595,344 Great Britain Dec. 2, 1947 599,055 Great Britain Mar. 3, 1948 OTHER REFERENCES Chem. Technology of Dyeing and Printing, by L. Diserens, translated by Wengraf and Baumann, published by Reinhold Publishing Co., 1948, New York city. Page 179.

Amer. Dye. Reporter for January 28,1946, page P55. 

1. PROCESS FOR THE COLORATION OF TEXTILE MATERIAL OF A CELLULOSE DERIVATIVE SELECTED FROM THE GROUP CONSISTING OF CELLULOSE ESTERS AND CELLULOSE ETHERS, WHICH COMPRISES IMPREGNATING THE MATERIAL WITH A SOLUTION OF AN ESTER OF A LEUCO VAT DYE IN A MIXTURE OF WATER AND AN ORGANIC LIQUID CONTAINING UREA, THE SAID MIXTURE OF WATER AND ORGANIC LIQUID BEING A SWELLING AGENT FOR THE CELLULOSE DERIVATIVE AND THEREAFTER STEAMING THE MATERIAL, CONVERTING THE ESTER TO THE PARENT VAT DYE, AND AGAIN STEAMING THE MATERIAL. 